NF-κB Is Required for Apoptosis Prevention during Herpes Simplex Virus Type 1 Infection

Abstract

Herpes simplex virus type 1 (HSV-1) is a large, enveloped, double-stranded DNA virus with a genome of approximately 150 kbp that encodes over 80 proteins, many of whose functions are still unknown (reviewed in reference 48). Productive HSV-1 infection occurs in a sequentially ordered cascade in which ␣ (immediate-early or IE) proteins precede the synthesis of ␤ (early or E) and ␥ (late or L) proteins (22,23). During the course of lytic infection, HSV-1 takes over the host cell, subjugating the cell's biomolecular synthesis machinery to serve its own reproduction. Cells react to viral infection by attempting to block viral replication, undergoing apoptosis, or by signaling neighboring cells to activate antiviral systems (reviewed in reference 31).The interplay between HSV-1 and its host involves numerous factors, and the virus employs several mechanisms to combat the many antiviral responses enacted by an infected cell. One of the most dramatic cellular responses to viral infection is the induction of apoptosis or programmed cell death. Apoptosis is characterized by cell shrinkage, membrane blebbing, redistribution of phosphatidylserine to the outer leaflet of the plasma membrane, fragmentation of nuclei (karyorrhexis), chromosomal DNA (pyknosis), and oligosomal DNA laddering (29,30,58). These structural modifications are a consequence of the activation of effector (executioner) caspases (cysteine aspartases), one of which is caspase 3, and the cleavage of poly(ADP-ribose) polymerase (PARP) and structural proteins (29,30,39,57,58). Apoptosis functions to limit virus spread by preventing viral replication, saving other cells from infection (34). HSV-1 has developed a mechanism to counteract this antiviral cell death process (3).The interaction of HSV-1 with its host cell results in the triggering of the apoptotic cell death program (2,4,33). During infection by wild-type HSV-1, caspase 3 is activated (4), the death factor DFF45 is completely cleaved (4), and phosphatidylserine is flipped from the inner to the outer membrane leaflet (25), indicating that replication-competent HSV-1 triggers the apoptosis death program and infected cells are actively in an apoptotic state. However, cells infected with wild-type HSV-1 do not show features of apoptosis, because infected cell proteins produced between 3 and 6 h postinfection (hpi), termed the apoptosis "prevention window" (4), prevent the process from killing the cells (4). Thus, human HEp-2 cells infected with either (i) viruses containing a deletion in the key viral regulators ICP4 or ICP27 or (ii) wild-type virus plus the addition of cycloheximide (CHX) at the time of infection, die by apoptosis (2,33,37). Although most recent efforts have focused on identifying viral gene products involved in apopto-* Corresponding author. Mailing address:

Induction of interleukin-6 in human retinal epithelial cells by an attenuated Herpes simplex virus vector requires viral replication and NFκB activation

“…The activation of NF-κB at 3-4 h post-infection in ARPE-19 cells is similar to the timing of NF-κB activation in other cell types infected with HSV (Patel et al 1998;Amici et al 2001;Goodkin et al 2003;Taddeo et al 2003;Amici et al 2006). A transient activation of NF-κB that occurs immediately upon infection has also been reported to occur in a human keratinocyte cell line (HaCaT) (Amici et al 2006).…”

“…In macrophages, where NF-κB activation was required for induction of RANTES, deletion of the ICP-0 gene prevented induction whereas deletion of ICP-4, ICP-27, and ICP-22 had no effect (Melchjorsen et al 2002;Melchjorsen and Paludan 2003). In contrast, ICP-27 appears to be required for NF-κB activation in Hep-2 and CV-1 cells (Goodkin et al 2003;Hargett et al 2006). These results indicate that mechanism of activation of NF-κB depends on the cell type.…”

The effects of trichostatin A on the oncolytic ability of herpes simplex virus for oral squamous cell carcinoma cells

“…Goodkin et al 26 proposed that NF-kB was required as an antiapoptotic factor in prolonging functional cell Trichostatin A and oncolytic virotherapy with HSV-1 T Katsura et al survival, and thus efficient viral replication. Gregory et al 34 examined the replication of HSV-1 in cell lines with deletions of IKK1 or IKK2 and found an 86-94% loss of viral yield compared with normal cells.…”

“…14 To determine whether the HSV-1 mutant could activate NF-kB, SAS cells were infected with R849 at an MOI of 2, and cytoplasmic and nuclear extracts were subjected to an immunoblot analysis using antibodies against p65. As PARP was expressed in the nucleus, 26 the blotted membranes were also reacted with anti-PARP antibody. The expression of p65 was increased in the nucleus from 6 h after infection and became remarkable at 12 h (Figure 1a).…”

“…18 With regard to HSV infections, NF-kB is activated early during an HSV-1 infection, translocates to the nucleus 24,25 and prevents virus-induced early apoptosis of infected cells to complete its replication cycle. [25][26][27] Whether an HDACi that activates NF-kB could affect the replication of oncolytic HSV-1 mutants has not been investigated. In this study, we examined the effects of TSA on the NF-kB activity of oral SCC cells and antitumor activity of g 1 34.5 gene-deficient mutants.…”